In multi-channel projection displays, such as used for example in simulation environments, externally generated test pattern grids are generally used as references for the mechanical and geometric (electrical) alignment of the many display channels. These test patterns are designed to represent the location of significant landmarks that may be pre-calculated positions, according to the type of screen (flat, curved, front, rear, etc.), eye-points and position of the projectors.
Many solutions exist to visualize the pre-calculated points to guide display alignment: one can mark “invisible” dots using UV-paint, one can use a slide-projector to project these points, one can install small LED's or fiber optic strands in the screen surface for example. None of these solutions is ideal: they can't be used on all types of screens, they require a complicated setup which may include direct access to the screen surface, several are inaccurate and expensive to correct, and many can only be used in a dark environment.